The investigation to be carried out in the coming year will be concerned with studies of the role of the kidney in erythropoietin (ESF) production. Our hypothesis which is the basis of this proposal is that stimuli such as reduction in renal blood flow, hypoxic hypoxia and cobalt stimulate kidney production of erythropoietin by increasing prostaglandins PGE-2 in kidney as a first step. The prostaglandins which are released in the kidney activate adenyl cyclase to increase cyclic 3',5' adenosine monophosphate (cyclic AMP) in the kidney. Cyclic AMP probably triggers the activation of a factor in the light mitochrondrial fraction of the kidney which acts either through an enzymatic mechanism or a proerythropoietin to increase the generation of erythropoietin. We further postulate that the beta adrenergic nervous system is triggered by these stimuli to generate erythropoietin via the adenyl cyclase system. Our objectives for the next year are: 1) to continue studies to determine the levels of prostaglandins E and erythropoietin in renal venous blood of dogs following exposure to hypoxia, reduction in renal flow, cobalt injections and beta adrenergic stimulation; 2) the effects of inhibitors of prostaglandins synthesis such as indomethacin and beta adrenergic blocking drugs such as dl-propranolol and butoxamine will also be studied as to their effects in antagonizing erythropoietin production following the application of the above erythropoietic stimuli; 3) the direct effects of renal prostaglandin PGE-2, PGA-2 and PGF2 on production of erythropoietin in the isolated perfused dog kidney and the ex-hypoxic polycythemic mouse assay will also be studied; 4) studies on the cytological localization of erythropoietin in the hypoxic monkey and anemic human kidney will be continued; and 5) studies on the further development of a radioimmunoassay for erythropoietin will also be continued during this next year.